DESCRIPTION: (adapted from the applicants abstract) The overall goal of this proposal is to define the molecular mechanisms underlying the appropriate expression of uterine endometrial genes whose products are essential to this tissue's growth, differentiation and functions during pregnancy. The applicant will continue to utilize the gene encoding the progesterone (P)-regulated transplacental iron transport protein, uteroferrin (Uf) as a paradigm for pregnancy-associated endometrial gene transcription since its expression is differentially regulated by the steroid hormones E and P as well as by a variety of nuclear proteins whose expression levels and/or DNA-binding activities in the endometrium vary with pregnancy or carcinoma status. The PI has recently cloned a newly discovered member of the Sp-family of transcription factors termed Basic Transcription Element Binding (BTEB) protein from pregnant endometrium (porcine model) and which transactivates the Uf gene in vivo and in vitro. The goal of the proposed study is to test the hypothesis that BTEB plays a pivotal role in uterine endometrial growth and differentiation via its functional interactions with the progesterone receptor (PR) and its regulation of "downstream target" genes. We postulate that BTEB, in the P-dominated endometrium (as in pregnancy) mediates endometrial differentiation, but functions as a growth stimulator, in the absence of P. The specific aims of this application are: 1. To elucidate the transcriptional and post-transcripitonal mechanisms that regulate BTEB mRNA and protein synthesis in endometrial cells; 2. To examine if functional interactions exist between BTEB and PR to modulate gene transcription, using the Uf gene promoter which contains binding sites for BTEB and PR as the response gene; 3. To elucidate the biological consequences of BTEB expression and of BTEB interactions with PR, in endometrial epithelial cells, by analysis of the growth parameters, secretory activity and expression of specific differentiation markers of human endometrial carcinoma HEC-1A cells stably transfected with BTEB and/or PR; and 4. To identify BTEB "downstream" genes using endometrial cells stably transfected with a BTEB expression lasmid. The significance of this research lies in providing a basic understanding of the molecular processes that underlie uterine endometrial growth and differentiation. The demonstration that gene activity in normal pregnancy endometrial cells is mediated by BTEB and PR, whose interaction is anticipated to be lacking or limited in abnormal endometrial (carcinoma) cells may provide novel strategies for treatment of abnormal conditions of human pregnancy and other human gynecological diseases.